U.S. Pat. No. 3,457,799, issued Jul. 29, 1969, describes a motor vehicle steering column having a column shaft assembly for transferring steering torque and including a first shaft having a polygonal solid end telescopically disposed in a correspondingly polygonal tubular end of a second shaft. Plastic is in situ injection molded into a clearance between the polygonal ends and into a transverse bore through the ends. When solidified, the plastic effects an angularly and linearly rigid connection between the polygonal ends which persists until the steering column experiences an energy absorbing collapse event during which the plastic in the clearance between the shaft ends defines a bearing for minimizing friction. In applications where the column shaft assembly normally experiences repeated extend/retract cycles, e.g. a length adjustable steering column, an in situ injection molded bearing such as described in the aforesaid U.S. Pat. No. 3,457,799 may be susceptible to wear and abrasion.
U.S. Pat. No. 4,509,775, issued Apr. 9, 1985 and assigned to the assignee of this invention, describes an intermediate shaft assembly for transferring steering torque between a column shaft assembly and a steering gear in a motor vehicle steering system. The intermediate shaft assembly includes a first shaft having a polygonal solid end telescopically disposed in a correspondingly polygonal tubular end of a second shaft and an arched spring in a cavity in the solid end bearing against a wall of the tubular end. The spring urges the polygonal ends in relative linear separation to a substantially zero linear clearance relationship for torque transfer without angular lash. During multiple extend/retract cycles characteristic of intermediate shaft assemblies in motor vehicle steering systems, the spring maintains the zero clearance relationship between the shaft ends while sliding back and forth relative to the wall of the tubular end.
A shaft assembly according to this invention is particularly suited for torque transfer in applications where multiple extend/retract cycles are normally experienced and is an improvement over the shaft assemblies described in the aforesaid U.S. Pat. Nos. 3,457,799 and 4,509,775.